<template>
	<ul class="list">
		<li class="item" 
			v-for="item of letters" 
			:key="item"
			@click="handleLetterClick"
			@touchstart.prevent="handleTouchStart"
			@touchmove="handleTouchMove"
			@touchend="handleTouchEnd"
			:ref="item"
		>{{item}}</li>
	</ul>
</template>

<script>
export default{
	name:'CityAlphabet',
	props:{
		cities:Object
	},
	computed:{
		letters:function(){
			const letters = []
			for(let i in this.cities){
				letters.push(i)
			}
			return letters
		}
	},
	data(){
		return {
			touchStatus:false,
			startY:0,
			timer:null
		}
	},
	update(){
		this.startY = this.$refs['A'][0].offsetTop
	},
	methods:{
		handleLetterClick:function(e){
			this.$emit('change',e.target.innerText);
		},
		handleTouchStart:function(e){
			this.touchStatus = true
		},
		handleTouchMove:function(e){
			if(this.touchStatus){
				if(this.timer){
					clearTimeout(this.timer)
				}
				this.timer = setTimeout(()=>{
					const touchY = e.touches[0].clientY - 79
					const index = Math.floor((touchY - this.startY)/22)
					this.$emit('change',this.letters[index])
				},20)
			}
		},
		handleTouchEnd:function(e){
			
		}
	}
}
</script>

<style lang="stylus" scoped>
	.list
		display:flex
		flex-direction: column
		justify-content: center
		position: absolute
		right: 0
		top: 1.58rem
		width: .4rem
		bottom: 0
		.item
			text-align: center
			line-height: .44rem
			color:#00bcd4

</style>
